Center Lightbox with jQuery

center_box.js

//Center Lightbox
  	function center_box(){
			var body = $('body')[0];
			var box_height = $('#lightbox').height();
			var box_width = $('#lightbox').width();
			var screen_height = $(body).height();
			var screen_width = $(body).width();

			var top = (screen_height / 2) - (box_height / 2);
			var left = (screen_width / 2) - (box_width / 2);

			$('#lightbox').css('top', top);
			$('#lightbox').css('left', left);
		}
		$(document).ready(function(){
			center_box();
		});
		$(window).resize(function(){
			center_box();
		});